Preparation method of degassing film

Abstract

The invention provides a preparation method of a degassing membrane, which comprises the following steps: uniformly stirring and mixing a high-molecular polymer and a water-soluble diluent under the condition of 120-160 DEG C to prepare a homogeneous solution at the temperature of 120-160 DEG C; respectively feeding the homogeneous solution and the core liquid into a metering pump under the condition of a characteristic gas atmosphere, carrying out core liquid mass transfer treatment on the homogeneous solution under the condition of the characteristic gas atmosphere at the temperature of 20-50 DEG C, and carrying out injection extrusion molding on a product from a spinning nozzle to obtain the molded degassing film. By adopting the technical scheme of the invention, the water-soluble diluent is selected as the diluent of the high-molecular polymer, and the mass transfer treatment process is added in the process, so that the water-soluble diluent and the core liquid generate substance exchange, the degassing film has the advantages of good mechanical property and high porosity, the degassing efficiency and other properties of the degassing film are improved, and the service life of the degassing film is prolonged. And the water-soluble diluent can be prevented from remaining on the surface of the formed degassing film, and meanwhile the production cost of the degassing film can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of degassing membrane preparation technology, and in particular relates to a degassing membrane preparation method. Background Art

[0002] Degassing membrane is a membrane separation product that uses the diffusion principle to remove gaseous substances such as carbon dioxide, oxygen, and nitrogen from liquids. Degassing membranes are often used in water purification processes in the fields of petrochemical production, thermal power generation, and microelectronic device manufacturing. The degassing membrane is equipped with a large number of microporous hollow fibers. Water molecules cannot pass through the micropores of the hollow fibers, but gas molecules can. When working, water flows through the inside of the hollow fibers under a certain pressure, and the outside of the hollow fibers continuously extracts the gas under the action of the vacuum pump, forming a certain negative pressure. The gas molecules in the water continuously overflow through the micropores of the hollow fibers. Therefore, in the degassing membrane structure, the microporous hollow fibers serve as the interface for separating the gas phase and the liquid phase, realizing the mass transfer between the gas phase and the liquid phase.

[0003] At present, the preparation methods of degassing membranes mainly include several process methods such as non-solvent induced phase separation, melt stretching and thermally induced phase separation. Among them, the non-solvent induced phase separation method refers to dissolving the polymer in a strong polar solvent to form a homogeneous solution, and then adding an extractant that is miscible with the solvent to extract the solvent to form a two-phase structure with the polymer as the continuous phase and the solvent as the dispersed phase. After removing the solvent, the obtained degassing membrane has a hollow structure due to the diffusion mass transfer process between the solvent and the extractant, and the mechanical properties of the degassing membrane are poor, and it is still not put into practical use; the melt stretching method refers to melting and extruding the polymer, and after recrystallization, a lamellar structure arranged along the fiber axis is formed. During the post-stretching process, the lamellar structure separates to form pores, and finally the pore structure is fixed by heat treatment to form a microporous hollow fiber membrane degassing membrane. The melt stretching method often uses highly crystalline polymers as raw materials. The hollow fiber membranes prepared have high mechanical strength and no excess impurities remain during the preparation process. They are suitable for degassing ultrapure water. However, the degassing membranes prepared by the melt stretching method have the disadvantage of low porosity. Porosity is an important indicator for evaluating the performance of degassing membranes. When degassing membranes with low porosity are working, the removal efficiency of gaseous substances such as oxygen and carbon dioxide is low, making it difficult for the melt stretching method to be widely promoted and applied. The thermally induced phase separation method is to dissolve the polymer in a high-boiling point, low-volatile diluent to form a homogeneous solution, and then reduce the porosity to form a homogeneous solution. During the cooling process, the homogeneous solution undergoes phase separation, the polymer forms a continuous phase, and the diluent forms a dispersed phase. Finally, the diluent is extracted and removed by an extractant to obtain a microporous hollow fiber degassing membrane. The microporous hollow fiber degassing membrane prepared by thermally induced phase separation has the advantages of a small pore size distribution range and high porosity, and has good mechanical strength. However, since an extractant is required to extract the diluent at the end of the thermally induced phase separation process, the diluent cannot be completely extracted under normal circumstances, and part of the diluent will remain on the surface of the degassing membrane, affecting the quality of the degassing membrane.

[0004] Since the above-mentioned methods for preparing degassing membranes each have their own advantages and disadvantages, researchers at home and abroad have tried to combine the two methods to prepare degassing membranes. For example, the patent document with the publication number "CN104707490A" discloses a method for preparing an ultrafine polyolefin degassing membrane, in which the polyolefin is heated and stirred in a diluent system until it is completely dissolved to form a uniform solution and extruded, and then stretched under the action of an electric field force to form ultrafine fibers. The formed ultrafine fibers are cooled with a liquid or solid cooling medium until phase separation and solidification of the high polymer content phase occur, and the cooling medium does not dissolve the polymer and does not chemically react with the polymer. The asymmetric fiber membrane prepared by this patented technical solution has an easily adjustable diameter, a dense cortex and a sponge-like open-pore microporous support layer. However, in the process, an extractant is still required to extract and remove the residual diluent. In the preparation process of the degassing membrane, the relevant personnel cannot know the content of the residual diluent, nor can the residual diluent be completely removed, which in turn affects the quality of the degassing membrane.

[0005] Studies have shown that the performance of degassing membranes depends essentially on the mass transfer rate of microporous hollow fibers. To increase the mass transfer rate of microporous hollow fibers in degassing membranes as much as possible, the gas phase should completely fill the membrane pores. When the membrane pores are wetted, the mass transfer resistance of the microporous hollow fiber membrane increases, which correspondingly increases the resistance of gas molecules passing through the hollow fiber membrane pores, causing the performance of the degassing membrane to decline and affecting the service life of the degassing membrane. Therefore, in order to improve the performance of the degassing membrane, the anti-wetting performance of the degassing membrane pores must first be improved. The anti-wetting performance of the degassing membrane pores is closely related to the contact angle and surface energy of the gas-liquid interface. The contact angle of the gas-liquid interface is a key indicator of the degree of wetting. In the case of solid-liquid contact, the contact angle is defined as the angle formed at the intersection of the gas-liquid interface and the solid-liquid interface. When the contact angle is greater than 90°, it indicates that the liquid is dense on the surface and has low wettability; and the lower the surface energy, the less susceptible the degassing membrane is to moisture. The corresponding degassing performance of the degassing membrane is also excellent. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a degassing membrane.

[0007] The present invention is achieved through the following technical solutions.

[0008] The present invention provides a method for preparing a degassing membrane, comprising the following steps:

[0009] Step 1: uniformly stirring and mixing the high molecular polymer and the water-soluble diluent at 120-160° C. to obtain a homogeneous solution at a temperature of 120-160° C.;

[0010] Step 2: The homogeneous solution and the core liquid are respectively sent into the metering pump under the characteristic gas atmosphere conditions, and then the homogeneous solution is subjected to the core liquid mass transfer treatment at a temperature of 20-50°C under the characteristic gas atmosphere conditions, and the product is ejected and extruded from the spinneret to obtain a shaped degassing membrane.

[0011] The concentration of the high molecular weight polymer in step 1 is 5-25wt%.

[0012] The high molecular polymer in step 1 is polytetrafluoroethylene, polypropylene, polysulfone or polyvinylidene fluoride.

[0013] The water-soluble diluent in step 1 is propylene carbonate, gamma-butyrolactone, triethyl phosphate or Polarclean.

[0014] The core liquid in step 2 is pure water, glycerol, propylene carbonate or gamma-butyrolactone.

[0015] The degassing film preparation method further comprises the following steps: cooling the shaped degassing film obtained in step 2 and then winding it on the outer peripheral surface of the drum.

[0016] The degassing membrane preparation method further comprises the following steps:

[0017] Step 1: Soak the formed degassing membrane obtained in step 2 in pure water, remove the residual water-soluble diluent by pure water, and then take it out;

[0018] Step 2: first soak the formed degassing membrane in an alkaline solution, then take it out, wash it with deionized water, and then naturally ventilate and dry the formed degassing membrane and naturally cool it to 20°C;

[0019] Step 3: Preliminarily uniformly mix alkylsilane and n-hexane to obtain a mixed solution, and then soak the formed degassing membrane in the mixed solution and then take it out to obtain a modified degassing membrane.

[0020] The concentration of the mixed solution in step 3 is 1-5%, and the immersion time of the formed degassing membrane in the mixed solution is 12-36 hours.

[0021] The alkylsilane in step 3 refers to octadecyltrimethoxysilane, octadecyltrichlorosilane, hexadecyldimethylchlorosilane, hexadecyltriethoxysilane or octadecyldimethylchlorosilane.

[0022] The degassing membrane preparation method further comprises the following steps: firstly, using n-hexane to clean and remove the alkyl silane remaining on the surface of the formed degassing membrane, and after the n-hexane is volatilized, drying the formed degassing membrane.

[0023] The beneficial effects of the present invention are as follows: by adopting the technical scheme of the present invention, the melt stretching method and the thermally induced phase separation method are combined, and a water-soluble diluent is selected as the diluent for the high molecular polymer. The process method combines the advantages of the melt stretching method and the thermally induced phase separation method respectively, and adds a mass transfer treatment process in the process, so that the water-soluble diluent and the core liquid produce material exchange, so that the microporous hollow fiber degassing membrane has a continuous network structure section, and at the same time has the advantages of good mechanical properties and high porosity, thereby improving the degassing efficiency and other properties of the degassing membrane. Moreover, since the water-soluble diluent can be completely dissolved in water, in the degassing membrane preparation process of the present invention, the pure water immersion method can be used to completely remove the residual water-soluble diluent, thereby avoiding the water-soluble diluent from remaining on the surface of the formed degassing membrane, and at the same time can reduce the production cost of the degassing membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional structural photograph of a microporous hollow fiber degassing membrane obtained in Example 1 of the present invention;

[0025] Figure 2 This is a comparison diagram of the anti-wetting performance of the degassing membrane prepared in Example 1 of the present invention before and after the hydrophobic modification treatment;

[0026] Figure 3 It is a structural schematic diagram of the degassing membrane preparation device of the present invention;

[0027] Figure 4 is a comparison photograph of the contact angle of the gas-liquid interface of the degassing membrane prepared in Example 2 of the present invention before and after the hydrophobic modification treatment;

[0028] Figure 5 It is a schematic diagram of detecting the deoxygenation efficiency of the degassing membrane of the present invention.

[0029] In the figure: 1-twin-screw extruder, 2-metering pump, 3-spinneret, 4-melt kettle, 5-core liquid kettle, 6-winder, 7-coagulation bath. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0031] like Figures 1 to 5 As shown, the present invention provides a method for preparing a degassing membrane, comprising the following steps:

[0032] Step 1: uniformly stirring and mixing the high molecular polymer and the water-soluble diluent at 120-160° C. to obtain a homogeneous solution at a temperature of 120-160° C.;

[0033] Step 2: The homogeneous solution and the core liquid are respectively sent into the metering pump under the characteristic gas atmosphere conditions, and then the homogeneous solution is subjected to the core liquid mass transfer treatment at a temperature of 20-50°C under the characteristic gas atmosphere conditions, and the product is ejected and extruded from the spinneret to obtain a shaped degassing membrane.

[0034] The technical scheme of the present invention is adopted to combine the melt stretching method with the thermally induced phase separation method, and a water-soluble diluent is selected as the diluent for the high molecular polymer. The process method combines the advantages of the melt stretching method and the thermally induced phase separation method, and adds a mass transfer treatment process in the process, so that the water-soluble diluent and the core liquid produce material exchange, so that the microporous hollow fiber degassing membrane has a continuous network structure section, and at the same time has the advantages of good mechanical properties and high porosity, thereby improving the degassing efficiency and other properties of the degassing membrane. In addition, since the water-soluble diluent can be completely dissolved in water, in the degassing membrane preparation process of the present invention, the pure water immersion method can be used to completely remove the residual water-soluble diluent, thereby avoiding the water-soluble diluent from remaining on the surface of the formed degassing membrane, and at the same time can reduce the production cost of the degassing membrane.

[0035] like Figure 1 As shown, the microporous hollow fiber degassing membrane prepared by the process of the present invention has a continuous mesh structure in cross section and good permeability.

[0036] Specifically, the concentration of the high molecular polymer in step one is preferably 5-25wt%. The high molecular polymer in step one is polytetrafluoroethylene, polypropylene, polysulfone or polyvinylidene fluoride. The water-soluble diluent in step one is propylene carbonate, gamma-butyrolactone, triethyl phosphate or Polarclean. The core liquid in step two is pure water, glycerol, propylene carbonate or gamma-butyrolactone. The degassing membrane preparation method also includes the following steps: after the molded degassing membrane obtained in step two is cooled, it is wound on the outer peripheral surface of the drum. The characteristic gas is nitrogen. Cooling the molded degassing membrane means: providing a coagulation bath, adding pure water at a temperature of 20°C to the coagulation bath, first immersing the molded degassing membrane in pure water from one side of the coagulation bath, and then taking out the molded degassing membrane from the other side of the coagulation bath.

[0037] In addition, the degassing membrane preparation method further comprises the following steps:

[0038] Step 1: Soak the formed degassing membrane obtained in step 2 in pure water, remove the residual water-soluble diluent by pure water, and then take it out;

[0039] Step 2: first soak the formed degassing membrane in an alkaline solution, then take it out, wash it with deionized water, and then naturally ventilate and dry the formed degassing membrane and naturally cool it to 20°C;

[0040] Step 3: Preliminarily uniformly mix alkylsilane and n-hexane to obtain a mixed solution, and then soak the formed degassing membrane in the mixed solution and then take it out to obtain a modified degassing membrane.

[0041] Specifically, the temperature of the pure water in step 1 is preferably 60°C, and the immersion time of the molded degassing membrane in the pure water is 12-36 hours. The concentration of the alkaline solution in step 2 is 0.2-1mol / L, and the immersion time of the molded degassing membrane in the alkaline solution is 1-2 hours. The alkaline solution in step 2 is sodium hydroxide, potassium hydroxide or lithium hydroxide. The concentration of the mixed solution in step 3 is 1-5%, and the immersion time of the molded degassing membrane in the mixed solution is 12-36 hours. The alkylsilane in step 3 refers to octadecyltrimethoxysilane, octadecyltrichlorosilane, hexadecyldimethylchlorosilane, hexadecyltriethoxysilane or octadecyldimethylchlorosilane. The degassing membrane preparation method also includes the following steps: first use n-hexane to clean and remove the residual alkylsilane on the surface of the molded degassing membrane, and after the n-hexane is volatilized, the molded degassing membrane is dried. The formed degassing film is placed in an oven for drying. The temperature in the oven is 60-100°C and the drying duration is 10-30 minutes.

[0042] According to the technical scheme of the present invention, after the formed degassing membrane is treated with pure water, alkaline solution, and a mixed solution of alkylsilane and n-hexane in sequence, the hydrophobic property of alkylsilane is utilized to cause the alkylsilane to undergo hydrolysis and condensation reaction with the hydroxyl groups on the surface of the hollow fiber degassing membrane treated with immersion in the alkaline solution to form a self-assembled hydrophobic surface, thereby obtaining a modified degassing membrane, significantly improving the anti-wetting property of the degassing membrane, and the surface of the modified degassing membrane has good hydrophobicity, thereby improving the degassing efficiency and stability of the membrane. Compared with conventional degassing membranes, the modified degassing membrane has a longer service life, which is conducive to promotion and application in the water purification industry.

[0043] like Figure 2 As shown, when the conventional degassing membrane that has not been hydrophobically modified is initially working, there is no liquid filling on the membrane pore surface, and the oxygen flux is greater than 30L / min. As the operating time increases, the oxygen flux gradually decreases. After 65 hours of continuous operation, the oxygen flux of the conventional degassing membrane that has not been hydrophobically modified rapidly drops to 21L / min, while the oxygen flux of the modified degassing membrane tends to be stable with a smaller decline, indicating that the modified degassing membrane has better anti-wetting properties and a longer service life.

[0044] In addition, if Figure 3As shown, the present invention also provides a degassing film preparation device, including a twin-screw extruder 1, a metering pump 2 and a spinneret 3, the twin-screw extruder 1, the metering pump 2 and the spinneret 3 are connected in series in sequence, the input end of the twin-screw extruder 1 is also connected to a melt kettle 4, and the input end of the metering pump 2 is also connected to a core liquid kettle 5.

[0045] Specifically, the degassing film preparation device further includes a winder 6, which is arranged behind the spinneret 3 according to the direction of material flow. The degassing film preparation device further includes a coagulation bath 7, which is arranged between the spinneret 3 and the winder 6 according to the direction of material flow.

[0046] The technical effects of the present invention are specifically described below through the following two embodiments.

[0047] Embodiment 1:

[0048] First, 10wt% polyvinylidene fluoride and triethyl phosphate are added to the melt kettle and mixed and stirred at a stirring temperature of 150°C. Then, pure water is added to the core liquid kettle and the temperature is set to 25°C. All pipeline heating and screw heating are turned on and the temperature is set to 150°C. Pure water at room temperature is added to the coagulation bath. After the homogeneous solution is completely dissolved, the stirring of the melt kettle is stopped, and nitrogen is respectively introduced into the melt kettle and the core liquid kettle. The core liquid kettle valve is opened and the screw, metering pump and winder are turned on at the same time. The homogeneous solution and the core liquid are respectively introduced into the metering pump under a nitrogen gas atmosphere. Then, the homogeneous solution is subjected to a core liquid mass transfer treatment at a temperature of 20-50°C under a nitrogen gas atmosphere. The product is then ejected and extruded from a spinneret to obtain a molded degassing film. The molded degassing film is then cooled and cleaned by pure water in the coagulation bath to completely dissolve the water-soluble diluent in the pure water, thereby avoiding the water-soluble diluent remaining on the surface of the degassing film.

[0049] Subsequently, the prepared shaped degassing membrane was soaked in pure water for 12 hours and then taken out, and then placed in a sodium hydroxide solution with a concentration of 0.5 mol / L for alkaline treatment for 1 hour, then taken out and repeatedly rinsed with deionized water, and then the shaped degassing membrane was soaked in a solution of 2% hexadecyltriethoxysilane and n-hexane for 12 hours and taken out to obtain a modified degassing membrane. Finally, the hexadecyltriethoxysilane remaining on the surface of the modified degassing membrane was removed with n-hexane, and the membrane was placed in a fume hood. After the n-hexane was completely volatilized, the modified degassing membrane was placed in an oven at a temperature of 80°C and continuously dried for at least 20 minutes before being taken out.

[0050] Embodiment 2:

[0051] First, 8 wt % of polyvinylidene fluoride and propylene carbonate are added to the melt kettle and mixed and stirred at a stirring temperature of 130°C. Then, glycerol is added to the core liquid kettle, and the temperature in the core liquid kettle is set to 30°C. Then, all pipeline heating and screw heating are turned on, and the temperature is set to 140°C. After the homogeneous solution is completely dissolved, the stirring of the melt kettle is stopped, and nitrogen is respectively introduced into the melt kettle and the core liquid kettle. Room temperature pure water is added to the coagulation bath, the core liquid kettle valve is opened, and the screw, metering pump and winder are turned on at the same time. The homogeneous solution and the core liquid are respectively sent to the metering pump under a nitrogen gas atmosphere. Then, the homogeneous solution is subjected to a core liquid mass transfer treatment at a temperature of 20-50°C under a nitrogen gas atmosphere. The product is ejected and extruded from the spinneret, and the water-soluble diluent remaining on the surface of the product is removed by soaking in pure water for 8 hours. After the product is dried, a molded degassing film is obtained.

[0052] Subsequently, the formed degassing membrane was immersed in a potassium hydroxide solution with a concentration of 0.1 mol / L for 1 hour, and after being taken out, it was repeatedly rinsed with deionized water, and after its surface was dried, the formed degassing membrane was immersed in a solution of 4% octadecyltrimethoxysilane and n-hexane for 28 hours and taken out to obtain a modified degassing membrane. Then, n-hexane was used to remove the octadecyltrimethoxysilane remaining on the surface of the modified degassing membrane, and the membrane was placed in a fume hood and the n-hexane was completely volatilized. Then, the modified degassing membrane was placed in an oven at a temperature of 80°C and dried for 30 minutes.

[0053] The relevant performance indicators of the modified degassing membranes prepared in Example 1 and Example 2 are tested and calculated respectively. The test and calculation process is as follows, and the test and calculation results are shown in Table 1.

[0054] (1) Mechanical properties test

[0055] The mechanical properties of the modified degassing membrane were tested on an electronic universal testing machine according to national standards GB1039-79 and GB1040-79WD-10D. The tensile rate was 10 mm / min. The test results are shown in Table 1.

[0056] (2) Testing and calculation of porosity

[0057] First, the weight of the dried modified degassing membrane was weighed, and then the modified degassing membrane was immersed in the n-butanol solution for 24 h. Then, the weight of the modified degassing membrane after immersion was weighed again, and then the porosity of the modified degassing membrane was calculated according to the following formula:

[0058]

[0059] In the above formula, β is the porosity of the modified degassing membrane, mw is the weight of the dry modified degassing membrane, md is the weight of the modified degassing membrane after infiltration, pw is the density of n-butanol, pp is the density of the modified degassing membrane, and for Example 1 and Example 2, pw=8.8095 g / mL.

[0060] (3) Calculation of degassing efficiency

[0061] like Figure 5 As shown, the specific steps for testing the degassing efficiency are as follows:

[0062] Step 1: Wind the modified degassing membranes obtained in Example 1 and Example 2 to form a cylindrical degassing membrane assembly. For the convenience of calculation, the outer peripheral area of ​​the degassing membrane assembly is 0.65m 2 ;

[0063] Step 2: Provide a dissolved oxygen meter and use deionized water at a temperature of 20°C as the degassing liquid. First, detect and record the initial oxygen content in the degassing liquid. Then, send the degassing liquid to the degassing membrane assembly via a peristaltic pump and a dissolved oxygen meter at a flow rate of 1.2L / h. After the reading is stable, read and record the dissolved oxygen value Os. At the same time, send pure water at a temperature of 20°C to the degassing membrane assembly via the dissolved oxygen meter.

[0064] Step 3: Use nitrogen to purge the surface of the degassing membrane assembly, and use a vacuum pump to remove the gas flowing through the surface of the degassing membrane assembly, so that the vacuum degree on the surface of the degassing membrane assembly is always maintained at 0.1MPa. At this time, the degassing liquid begins to degas, and observe the changes in the dissolved oxygen meter readings. When the reading changes tend to be stable, read and record the dissolved oxygen value O e , the degassing efficiency can be calculated according to the following formula:

[0065]

[0066] (4) Test of contact angle of gas-liquid interface

[0067] The test steps of the contact angle of the gas-liquid two-phase interface are as follows: place the dry degassing membrane horizontally on the stage directly below the needle of the instrument syringe, adjust the baseline to coincide with the projection of the highest end of the sample on the screen, drop a drop of 2μL of deionized water on the surface of the degassing membrane, record the water drop before it contacts the membrane, test the change of the contact angle data after the water drop contacts the degassing membrane and record the corresponding data. The data results are recorded as follows: Figure 4 As shown, the contact angle of the gas-liquid interface of the conventional formed degassing membrane is 103°, while the contact angle of the gas-liquid interface of the modified degassing membrane is 144°.

[0068] (5) Calculation of oxygen flux

[0069] Under the condition of an ambient temperature of 20°C, the modified degassing membrane was cut and wound into a cylindrical modified degassing membrane, and the outer peripheral area of ​​the cylindrical modified degassing membrane was 0.1 m 2 , then oxygen is sent into the inner cavity of the cylindrical modified degassing membrane, and the gas volume flow rate of the modified degassing membrane is tested at least 3 times with a flow meter, and the arithmetic mean of each measurement value is taken as the oxygen flux value.

[0070] Table 1 Comparison of the performance of the modified degassing membranes obtained in Example 1 and Example 2

[0071] Technical indicators Embodiment 1 Embodiment 2 Degassing efficiency 91％ 85％ Tensile Strength 14.86Mpa 16.52Mpa Elongation at break 280％ 256％ Porosity 70％ 65％

[0072] It can be seen from Table 1 that the degassing efficiency of the modified degassing membranes prepared in Example 1 and Example 2 is greater than 85%, and the porosity is 70% and 65% respectively. The high porosity can increase the gas permeability, so the degassing efficiency is higher. In addition, the tensile strength of the modified degassing membrane is greater than 14.86MPa, and the elongation at break is greater than 256%, indicating that the modified degassing membrane prepared by the present invention has both good mechanical properties and excellent degassing performance.

Claims

1. A method for preparing a degassing membrane, Features: The following steps are involved: Step 1: uniformly stirring and mixing the high molecular polymer and the water-soluble diluent at 120-160° C. to obtain a homogeneous solution at a temperature of 120-160° C.; Step 2: The homogeneous solution and the core liquid are respectively sent into the metering pump under the characteristic gas atmosphere conditions, and then the homogeneous solution is subjected to the core liquid mass transfer treatment at a temperature of 20-50°C under the characteristic gas atmosphere conditions, and the product is ejected and extruded from the spinneret to obtain a shaped degassing membrane.

2. The method for preparing a degassing membrane according to claim 1, Features: The concentration of the high molecular weight polymer in step 1 is 5-25wt%.

3. The method for preparing a degassing membrane according to claim 1 or 2, Features: The high molecular polymer in step 1 is polytetrafluoroethylene, polypropylene, polysulfone or polyvinylidene fluoride.

4. The method for preparing a degassing membrane according to claim 1, Features: The water-soluble diluent in step 1 is propylene carbonate, gamma-butyrolactone, triethyl phosphate or Polarclean.

5. The method for preparing a degassing membrane according to claim 1, Features: The core liquid in step 2 is pure water, glycerol, propylene carbonate or gamma-butyrolactone.

6. The method for preparing a degassing membrane according to claim 1, Features: The degassing film preparation method further comprises the following steps: cooling the shaped degassing film obtained in step 2 and then winding it on the outer peripheral surface of the drum.

7. The method for preparing a degassing membrane according to claim 1, Features: The degassing membrane preparation method further comprises the following steps: Step 1: Soak the formed degassing membrane obtained in step 2 in pure water, remove the water-soluble diluent remaining on the surface of the degassing membrane by pure water, and then take it out; Step 2: first soak the formed degassing membrane in an alkaline solution, then take it out, wash it with deionized water, and then naturally ventilate and dry the formed degassing membrane and naturally cool it to 20°C; Step 3: Preliminarily uniformly mix alkylsilane and n-hexane to obtain a mixed solution, and then soak the formed degassing membrane in the mixed solution and then take it out to obtain a modified degassing membrane.

8. The method for preparing a degassing membrane according to claim 7, Features: The concentration of the mixed solution in step 3 is 1-5%, and the immersion time of the formed degassing membrane in the mixed solution is 12-36 hours.

9. The method for preparing a degassing membrane according to claim 7, Features: The alkylsilane in step 3 refers to octadecyltrimethoxysilane, octadecyltrichlorosilane, hexadecyldimethylchlorosilane, hexadecyltriethoxysilane or octadecyldimethylchlorosilane.

10. The method for preparing a degassing membrane according to claim 7, Features: The degassing membrane preparation method further comprises the following steps: firstly, using n-hexane to clean and remove the alkyl silane remaining on the surface of the formed degassing membrane, and after the n-hexane is volatilized, drying the formed degassing membrane.

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